In a commonly used three-color pixel system, taking a liquid crystal display (LCD) device as an example, each pixel unit is generally composed of three sub pixel units, i.e., a red (R) sub pixel unit, a green (G) sub pixel unit, and a blue (B) sub pixel unit. In a new four-color pixel system, one sub pixel unit is added to the traditional three-color pixel system, and thus a color performance of the four-color pixel system can be improved.
With the development of the four-color pixel system, the three-color to four-color conversion technology is basically mature, and the corresponding product has entered into actual using stage. However, since there is no effective white balance regulation technology for the product with the four-color pixel system, the display effect of the product is not desirable. As a result, the advantage of four-color pixel system is not fully played.
FIG. 1(a) shows Gamma curves of a four-color pixel system in the prior art, and FIG. 1(b) shows a standard Gamma curve when white color is displayed. As shown in FIG. 1(a), curves 1, 2, 3, and 4 are respectively Gamma curves of an LCD with a four-color pixel system when red color, green color, blue color, and white color are displayed. The standard Gamma curve when white color is displayed should fall within a range of ±0.2˜0.3 with 2.2 as a mid value, so that the brightness change of the white color is in accordance with the perceptual curve of eye, as shown in FIG. 1(b). The brightness change of the four curves as shown in FIG. 1(a) all seriously deviate from the aforesaid range at relatively high gray-scale values, and thus an over-bright display effect would be generated.
In a word, a white balance method of a four-color pixel system is needed so that the color displayed therein is in accordance with the perceptual curve of eye.